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Commit 54587653 authored by Dave Hansen's avatar Dave Hansen Committed by Ingo Molnar
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x86/mpx: Introduce new 'directory entry' to 'addr' helper function 



Currently, to get from a bounds directory entry to the virtual
address of a bounds table, we simply mask off a few low bits.
However, the set of bits we mask off is different for 32-bit and
64-bit binaries.

This breaks the operation out in to a helper function and also
adds a temporary variable to store the result until we are
sure we are returning one.

Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave@sr71.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20150607183704.007686CE@viggo.jf.intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent a1149fc8

arch/x86/include/asm/mpx.h

+0 −1
Original line number Diff line number Diff line
@@ -45,7 +45,6 @@ 
#define MPX_BNDSTA_TAIL		2

#define MPX_BNDCFG_TAIL		12

#define MPX_BNDSTA_ADDR_MASK	(~((1UL<<MPX_BNDSTA_TAIL)-1))

#define MPX_BT_ADDR_MASK	(~((1UL<<MPX_BD_ENTRY_TAIL)-1))



#define MPX_BNDCFG_ADDR_MASK	(~((1UL<<MPX_BNDCFG_TAIL)-1))

#define MPX_BNDSTA_ERROR_CODE	0x3

arch/x86/mm/mpx.c

+34 −7
Original line number Diff line number Diff line
@@ -576,29 +576,55 @@ static int mpx_resolve_fault(long __user *addr, int write) 
	return 0;

}



static unsigned long mpx_bd_entry_to_bt_addr(struct mm_struct *mm,

					     unsigned long bd_entry)

{

	unsigned long bt_addr = bd_entry;

	int align_to_bytes;

	/*

	 * Bit 0 in a bt_entry is always the valid bit.

	 */

	bt_addr &= ~MPX_BD_ENTRY_VALID_FLAG;

	/*

	 * Tables are naturally aligned at 8-byte boundaries

	 * on 64-bit and 4-byte boundaries on 32-bit.  The

	 * documentation makes it appear that the low bits

	 * are ignored by the hardware, so we do the same.

	 */

	if (is_64bit_mm(mm))

		align_to_bytes = 8;

	else

		align_to_bytes = 4;

	bt_addr &= ~(align_to_bytes-1);

	return bt_addr;

}



/*

 * Get the base of bounds tables pointed by specific bounds

 * directory entry.

 */

static int get_bt_addr(struct mm_struct *mm,

			long __user *bd_entry, unsigned long *bt_addr)

			long __user *bd_entry_ptr,

			unsigned long *bt_addr_result)

{

	int ret;

	int valid_bit;

	unsigned long bd_entry;

	unsigned long bt_addr;



	if (!access_ok(VERIFY_READ, (bd_entry), sizeof(*bd_entry)))

	if (!access_ok(VERIFY_READ, (bd_entry_ptr), sizeof(*bd_entry_ptr)))

		return -EFAULT;



	while (1) {

		int need_write = 0;



		pagefault_disable();

		ret = get_user(*bt_addr, bd_entry);

		ret = get_user(bd_entry, bd_entry_ptr);

		pagefault_enable();

		if (!ret)

			break;

		if (ret == -EFAULT)

			ret = mpx_resolve_fault(bd_entry, need_write);

			ret = mpx_resolve_fault(bd_entry_ptr, need_write);

		/*

		 * If we could not resolve the fault, consider it

		 * userspace's fault and error out.
@@ -607,8 +633,8 @@ static int get_bt_addr(struct mm_struct *mm, 
			return ret;

	}



	valid_bit = *bt_addr & MPX_BD_ENTRY_VALID_FLAG;

	*bt_addr &= MPX_BT_ADDR_MASK;

	valid_bit = bd_entry & MPX_BD_ENTRY_VALID_FLAG;

	bt_addr = mpx_bd_entry_to_bt_addr(mm, bd_entry);



	/*

	 * When the kernel is managing bounds tables, a bounds directory
@@ -617,7 +643,7 @@ static int get_bt_addr(struct mm_struct *mm, 
	 * data in the address field, we know something is wrong. This

	 * -EINVAL return will cause a SIGSEGV.

	 */

	if (!valid_bit && *bt_addr)

	if (!valid_bit && bt_addr)

		return -EINVAL;

	/*

	 * Do we have an completely zeroed bt entry?  That is OK.  It
@@ -628,6 +654,7 @@ static int get_bt_addr(struct mm_struct *mm, 
	if (!valid_bit)

		return -ENOENT;



	*bt_addr_result = bt_addr;

	return 0;

}